P2RX1 and cancer: To further delineate the upstream targets of BCAT1, we evaluated several potential signaling pathways downregulated in P2x1-null LICs, such as transcriptional misregulation in cancer, and we found that the Pbx3 mRNA level in P2x1-null LICs was significantly decreased to 10% of that in WT LICs (Fig. 3C).